Preservation of synthetic rubber with aromatic arsenites



Patented Apr. 12,

UNITED STATES l?ATEN-T OFFICE f This invention relate dienes v on where X is hydroge phenyl or methyl, w butadienoid polyme PRESERVATION F WITH AROMA ter,

poration of New Jersey N 0' Drawings Application M Serial No.- 657,34

5'Claims. (Cl.'26045.'95)

s to the preservation of (elastomeric) materials oadly as diene polymers ymers), and more particularly om the modified 1,3-diene polyformed from the polymerization with compounds of the n or methyl; and Yis CN, hich includes especially those rs kn own to the trade as Buna S (GRS), Buna N (GRN), Butyl (GRI), Chemigum, Hycar OR, etc. -di'enes and polychlorop "included within the sc An object of the inv cals which, although -as antioxidants for will outstandingly -p like materials; an from 1,3'-dienes,'ag fore vulcanization, further objectis which may be synthetic rubber sto'ck dis-coloration wh them are expose -,stil1 further obje protect the unvulcaniz copolymers. against the when suchpolymers' are subj temperatures during processin ';isito provide chemicals which h Litstanding...properties F -preservation... of .diene mers. Still other obje the following descripti "The elastomeric polybutarene (neoprene) arealso ope of the invention. ention'is to provide chemihaving practically no value natural rubber, nevertheless reserve said synthetic rubberd particularly those' derived ainst deterioration induced beby oxygen, heat, or light. A to provide a class of compounds added-to White or light-colored s without producing bad en the compositions containing d to'the action of sunlight. A ct-is to provide :chemicals which ed diene-vinyl compound deleterious efiects of heat ected to elevated ave special and in' connection with 5 the -vinyl "compound copolycts will be apparent from 0 We have found that these objects may be attained if there is in thetic rubber an arc mat corporated into the synic ester of arsemous acid having the general formula senic, and R1, R2, and R 3 ssimllar aromatic. groups.

Another object arsenite,'tri-o-tolyl arsenite, 'tri-m tri-beta-naphthyl "'arsenite,

7 'methyl-2,6-ditert.

: sion copolymer rubbe arsenite are incorporated/in a usual manner. I placed inanoven at 212 F; 0f the same 'butadiene contains no triphenyl staining the qtriph'enyl Jarsenite' appearance while the unstabiliz method for pre SYN THETIC RUBBER TIG ARSENITES and ByronALHun- .-.assignors to 'United ew York, N. Y., acorarch-26, 1946, 2

Exemplary ofsuch chemicals are: triphenyl tolyl arsenite, -naphthyl arsenite, tri-xenyl arsenite, "tri-Z, 5-dimethyl ph'enyl'. arsenite, tri-o-cresyl arsenite, 'tri-(p-tertL-butyl phenyl) arsenite, tri- (2,4- ditert.-butyl phenyl) arsenite, and tri- (4- -buty1 phenyl) arsenite.

The chemicals of the invention may be made by any Imethodknown to the art. A convenient paring said arsenites is described by P. Fromm, Ber. 28, 620 (1895).

The various synthetic elastomers arexknown by the art to be produced in various manners, including 'those shown in U. S. Patents Nos. 1,973,000 and 1,938,731. The present invention, however, is not concerned with the particulars of producingthese elastomers but in their preservation, as aforesaid.

For the purpose of of the invention, ex styrene copolymer tri-p-tolyl 'arsenite, tri-alpha illustrating the best modes amples of a 1,3-butadiene- GRS) containing aromatic esters of arsenious acid are given for showing. the beneficial protective effects to be obtained from the use of suchchemicals; the parts .being kby weight:

Example 1 I To 100 parts ofbutadiene-25-styrene emulr, 2 parts of triphenyl a rubber mill in'the A sample of this rubber mix is along with a-sam-ple -styrene copolymer which .arsenite. Both samples were examined atterrai:hours. .Thesample conis; unchanged in ed sample forms acks on bending. e oven and heated inspected periodinstabilized sample a hard surface film which or Both samples are replaced in th at 212 F. for 400 hours, being cally. The surface film of the u becomes progressively harder and deeper whereas the sample containing triphenyl arsenite shows no visible deterioration and remains the same in appearance as the unaged polymer. Indeed, after 400 hours in the oven, the sample containing triphenyl arsenite remains unafiected and shows no visible degradation.

a product.

Example 2 In order to show the non-discoloring properties of aryl arsenites, synthetic rubber compositions are made up according to the following recipe:

Stock A Stock B Butadiene-styrene copolymer Zinc oxide Lithopone Whiting. Paraffin o' Sulfur Mercaptobenzothiazoi Tctramethyl thiuram monosulfi Trlphenyl arsemte Stocks A and B are mixed individually on a rubber mill and cured for 45 minutes at 45 lbs. steam pressure. Test pieces are out from both stocks and mounted for exposure to sunlight. Strips of cotton cloth and of lacquered tape are placed in contact with parts of the exposed test pieces for observation of staining characteristics. After 6 days exposure to the direct rays of the sun, stocks A and B are identical in color, each stock remaining light in color. The strips of cotton cloth and lacquered tape are not discolored by contact with either stock. These results conclusively show that triphenyl arsenate is nondiscoloring and non-staining, the stock containing the stabilizer bein equally good in color as that of the rubber stock containing no stabilizer;

It can be seen from these results that the compounds of this invention are extremely effective in overcoming the deterioration of diene-vinyl compound copolymers due to heat and oxidation. Furthermore, these results show that these deterioration inhibitors are essentially non-discoloring to white or light-colored stocks and are thereby suitable for use in either white or light colored synthetic rubber articles although they may be used in any color and type of rubber article.

The deterioration inhibitors of this invention may be used alone in the synthetic rubber composition or may be mixed with other preservatives, fillers, accelerators, vulcanizin agents, or compounding agents of any sort known to the art. The components of the synthetic rubber composition may be used in various ratios and it is not intended to limit the invention to the amounts of ingredients indicated in the examples given.

The age resistors of the invention may be incorporated into the synthetic rubber by milling or similar process, or by mixing with the synthetic rubber latex before or during coagulation, or application thereof may be made to the surface of the crude polymer or of the vulcanized The amount of the age resistor may vary, economical proportions ranging from 0.25 part to 5.0 parts by weight, based on 100 parts by weight of the elastomer base.

Synthetic rubber goods of various descriptions x CHz=( 3-Y where X is hydrogen and Y is a. radical from the class consisting of CN and phenyl, containing a compound having the general formula ORr where As represents arsenic, and R1, R2, and Rs each represent an aromatic hydrocarbon group, in a small but effective amount sufficient to \preserve the said rubbery polymer.

2. A rubbery 1,3-butadiene-styrene copolymer which comprises a compound having the general formula /0R, AS :0R: OR; where As represents arsenic, and Bi, R2, and Rs each represent an aromatic hydrocarbon group in a small but effective amount sufiicient to preserve the said copolymer.

3. A rubbery 1,3-butadiene-acrylonitrile copolymer which comprises a compound having the general formula where As represents arsenic, and R1, R2, and Rs each represent an aromatic hydrocarbon group in a small but effective amount sufllcient to preserve the said copolymer.

4. A rubbery 1,3-butadiene-styrene copolymer which comprises a triphenyl arsenite, in an amount sufficient to preserve the copolymer.

5. A rubbery 1,3-butadiene-acrylonitrile copolymer which comprises a triphenyl arsenite, in an amount suflicient to preserve the copolymer.

LOUIS H. HOWLAND. BYRON A. HUNTER.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Thwaites Mar. 23, 1943 

